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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        // 数字+数字  正常加减   --存在Nan则结果为NaN
        //数字+字符串  转化为字符串 进行拼接
        //null --0 undefinded -NaN
        //obj tostring 在拼接
        //boolean 和数值相加 01  和字符串相加 tostring 
        var a1=12-45;
        var a2=12+NaN;
        var a3=12+"你好";
        var a4=12+false;
        var a5=12-null;
        var a6=12-undefined;
        var a7={x:12}+45;
        var a8=[12,12,12,45]+412;
        console.log(a1);
        console.log(a2);
        console.log(a3);
        console.log(a4);
        console.log(a5);
        console.log(a6);
        console.log(a7);
        console.log(a8);
        //执行顺序 从左到右  跳级利用(  )进行加减

    </script>
</body>
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